Rotating machinery, turbo compressors, and refrigeration systems

Abstract

To improve the sealing performance in the sealing portion of a rotating body. [Solution] The seal structure 40 of the turbo compressor 100 has fins 71 to 73, and the axial distance between the lowest pressure fin 71 of the plurality of fins 71 and the highest pressure fin 72 of the plurality of fins 72 is defined as the first width W11, and the axial distance between the lowest pressure fin 72 of the plurality of fins 72 and the highest pressure fin 73 of the plurality of fins 73 is defined as the second width W12, and the second width W12 is narrower than the first width W13.

Description

Technical Field

[0001] The present disclosure relates to rotating machines, turbo compressors, and refrigeration systems.

Background Art

[0002] For example, a shaft seal device for a rotating machine having a stepped labyrinth seal is known (see Patent Document 1). The labyrinth seal described in Patent Document 1 includes a stepped first step portion provided along the axial direction on the outer peripheral surface of a rotating shaft, and a stepped second step portion provided on the inner peripheral surface of a labyrinth ring attached to a casing so as to follow the stepped shape of the first step portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, there has been room for improvement in improving the seal performance at the sealing portion of a rotating body.

[0005] An object of the present disclosure is to provide a rotating machine, a turbo compressor, and a refrigeration system in which the seal performance at the sealing portion of a rotating body is improved.

Means for Solving the Problems

[0006] A rotating machine according to one aspect of the present disclosure comprises a rotating body, a rotating shaft for driving the rotating body, a casing for housing the rotating body and the rotating shaft, and a sealing structure for sealing the gap between the rotating body and the casing, wherein in the casing, a high-pressure space is formed on one side in the axial direction of the rotating body, and a low-pressure space is formed on the other side in the axial direction of the rotating body, the outer circumferential surface of the rotating body has a first rotating surface, a second rotating surface, and a third rotating surface in order from the high-pressure space side, the distance of the first rotating surface from the rotating shaft is greater than the distance of the second rotating surface from the rotating shaft, the distance of the second rotating surface from the rotating shaft is greater than the distance of the third rotating surface from the rotating shaft, and the casing has a first fixed surface facing the first rotating surface, a second fixed surface facing the second rotating surface, a third fixed surface facing the third rotating surface, and from the first fixed surface toward the rotating body The seal structure includes one or more first fins that protrude outwards and are spaced apart in the axial direction, one or more second fins that protrude outwards from a second fixed surface toward a rotating body and are spaced apart in the axial direction, and one or more third fins that protrude outwards from a third fixed surface toward a rotating body and are spaced apart in the axial direction, wherein the seal structure includes the first fins, the second fins, and the third fins, the axial distance between the first fin on the lowest pressure side of the one or more first fins and the second fin on the highest pressure side of the one or more second fins is defined as the first width, the axial distance between the second fin on the lowest pressure side of the one or more second fins and the third fin on the highest pressure side of the one or more third fins is defined as the second width, and the second width is narrower than the first width.

[0007] In this embodiment of the rotating machine, the gap between fins can be narrowed in the axial direction of the rotating shaft, from the high-pressure space side to the low-pressure space side. The temperature on the high-pressure space side is higher than the temperature on the low-pressure space side. In this sealing structure of the rotating machine, the gap between fins on the low-pressure space side can be made narrower than the gap between fins on the high-pressure space side, preventing contact due to thermal contraction and improving sealing performance.

[0008] In a rotating machine according to one aspect of this disclosure, the rotating body may be a closed impeller. Generally, the seal diameter of the seal structure used in the shroud portion of a closed impeller is larger than the seal diameter of the seal structure on the rotating shaft (hereinafter referred to as the shaft seal). In the seal structure of the shroud portion of a closed impeller, the lower limit of the seal gap is larger than that of the shaft seal from the viewpoint of rotor dynamics and runout. Therefore, in the shroud portion of a closed impeller, the seal area becomes excessively large compared to the shaft seal, and the sealing performance tends to deteriorate. By adopting the seal structure of this disclosure in the shroud portion of a closed impeller, the deterioration of sealing performance can be suppressed.

[0009] In a rotating machine according to one aspect of this disclosure, the first length between the first fin on the lowest pressure side of one or more first fins and the end of the first rotating surface on the low pressure side, the second length between the second fin on the lowest pressure side of one or more second fins and the end of the second rotating surface on the low pressure side, and the third length between the third fin on the lowest pressure side of one or more third fins and the end of the third rotating surface on the low pressure side may be equal in the axial direction. By making the first length, second length, and third length equal in the seal structure, the sealing performance can be improved.

[0010] In a rotating machine according to one aspect of this disclosure, the first, second, and third rotating surfaces are parallel to the axial direction, and the cross-sections perpendicular to the axial direction of the first, second, and third rotating surfaces may be circular. Such a seal structure can improve sealing performance and reduce pressure imbalances in the circumferential direction due to the runout of the rotating body, thereby suppressing the generation of destabilizing forces.

[0011] A rotating machine according to one aspect of this disclosure may include a magnetic bearing that rotatably supports a rotating shaft. In a rotating machine equipped with a magnetic bearing, by adopting the above-described seal structure, the destabilizing force can be reduced by shortening the axial length of the seal structure, thus providing an advantageous structure for magnetic bearings, which are susceptible to excitation forces on the shaft.

[0012] The rotating machine according to one aspect of this disclosure may be a turbo compressor. In turbo compressors that generally operate at high absolute pressures, the above-described seal structure can be used to improve sealing performance and reduce destabilizing forces by shortening the axial length of the seal structure.

[0013] A refrigeration system according to one aspect of this disclosure may include the turbomachinery described above. In a refrigeration system that performs a refrigeration cycle circulating a refrigerant, the absolute pressure at which it operates becomes high. Therefore, by employing the above-described seal structure, it is possible to improve the sealing performance and reduce the destabilizing force by shortening the axial length of the seal structure. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view showing the impeller portion of a turbo compressor according to the first embodiment. [Figure 2] This is a cross-sectional view showing a seal structure according to the first embodiment. [Figure 3] This is an enlarged cross-sectional view showing the main part of the seal structure according to the first embodiment. [Figure 4] This is an enlarged cross-sectional view showing the main part of the seal structure according to the first embodiment. [Figure 5] This is a schematic diagram showing a refrigeration system equipped with a turbo compressor according to an embodiment. [Figure 6] This is a cross-sectional view showing a turbo compressor according to an embodiment. [Figure 7] This is a cross-sectional view showing a seal structure according to the second embodiment. [Modes for carrying out the invention]

[0015] Exemplary embodiments of the present disclosure will be described with reference to the attached drawings. In the attached drawings, the same or corresponding members or components are given the same or corresponding reference numerals. Also, hereinafter, duplicate descriptions of the same or corresponding members or components will be omitted. Also, in the drawings, the members or components are not necessarily drawn to scale. Therefore, those skilled in the art can arbitrarily determine specific dimensions by referring to the following non-limiting embodiments. Also, the following embodiments are illustrative rather than limiting the invention. Also, the features described in the embodiments and their combinations are not necessarily essential to the invention.

[0016] [Turbo Compressor 100] FIG. 1 is a cross-sectional view showing a portion of the impeller 10 of the turbo compressor 100 according to the first embodiment. The turbo compressor 100 may be, for example, a single-stage compressor, a two-stage compressor, or a multi-stage compressor with three or more stages. The turbo compressor 100 includes an impeller 10, a rotating shaft 20, a casing 30, and a seal structure 40.

[0017] The impeller 10 is a closed impeller. The impeller 10 is connected to the rotating shaft 20. The rotating shaft 20 is connected to the rotating shaft that is the drive source of the turbo compressor 100. The rotating shaft 20 is a drive shaft that drives the impeller 10. The casing 30 houses the impeller 10, the rotating shaft 20, and the bearings.

[0018] The impeller 10 includes a hub 11, blades 12, and a shroud 13. The hub 11 has a generally conical shape that expands in diameter from the front to the rear. In the axial direction of the rotating shaft 20, the side closer to the suction port is referred to as "front", and the side farther from the suction port is referred to as "rear". The hub 11 rotates integrally with the rotating shaft 20. The hub 11 may be hollow inside, excluding the portion around the axis and the outer edge portion, from the viewpoint of weight reduction.

[0019] The blade 12 is provided on the outer peripheral surface of the hub 11. The blade 12 projects radially outward from the outer peripheral surface 11a of the hub 11. The blade 12 is arranged in a spiral shape along the outer peripheral surface 11a of the hub 11. The shroud 13 is formed to cover the blade 12. In the radial direction of the rotary shaft 20, the shroud 13 is arranged apart from the outer peripheral surface 11a of the hub 11.

[0020] [Seal structure 40] FIG. 2 is a cross-sectional view showing the seal structure 40 according to the first embodiment. FIG. 3 is a cross-section showing an enlarged view of the main part of the seal structure 40 according to the first embodiment. The turbo compressor 100 includes a seal structure 40 for sealing the gap G between the outer peripheral surface 50 of the impeller 10 and the inner peripheral surface 60 of the casing 30. The seal structure 40 includes a stepped labyrinth seal. The impeller 10 is on the rotating side, and the casing 30 is on the fixed side. The impeller 10 is an example of a rotating body. The outer peripheral surface 50 of the impeller 10 may be the outer peripheral surface of the shroud 13.

[0021] Inside the casing 30, a high-pressure space HP and a low-pressure space LP are formed. The high-pressure space HP is formed on one side in the axial direction of the rotary shaft 20, and the low-pressure space LP is formed on the other side in the axial direction. The axial direction of the rotary shaft 20 may be the direction in which the center line C1 of the rotary shaft 20 extends.

[0022] The outer peripheral surface 50 of the impeller 10 has rotating surfaces 51 to 55. The rotating surfaces 51 to 55 are arranged in order in the axial direction. The rotating surface 51 is arranged closer to the high-pressure space HP, and the rotating surface 55 is arranged closer to the low-pressure space.

[0023] In the radial direction of the rotation axis 20, the distance between the center line C1 and the rotation surface 51 is greater than the distance between the center line C1 and the rotation surface 52. In the radial direction of the rotation axis 20, the distance between the center line C1 and the rotation surface 52 is greater than the distance between the center line C1 and the rotation surface 53. In the radial direction of the rotation axis 20, the distance between the center line C1 and the rotation surface 53 is greater than the distance between the center line C1 and the rotation surface 54. In the radial direction of the rotation axis 20, the distance between the center line C1 and the rotation surface 54 is greater than the distance between the center line C1 and the rotation surface 55. The rotation surfaces 51 to 55 are formed in a stepped shape.

[0024] The rotational planes 51-55 may be parallel to the center line C1. The cross-section of the rotational planes 51-55 perpendicular to the center line C1 is circular.

[0025] The inner circumferential surface 60 of the casing 30 has fixed surfaces 61 to 65. The fixed surfaces 61 to 65 are arranged sequentially in the axial direction. Fixed surface 61 is located closer to the high-pressure space HP, and fixed surface 65 is located closer to the low-pressure space.

[0026] In the radial direction of the inner circumferential surface 60, the distance between the center line C1 and the fixed surface 61 is greater than the distance between the center line C1 and the fixed surface 62. In the radial direction of the inner circumferential surface 60, the distance between the center line C1 and the fixed surface 62 is greater than the distance between the center line C1 and the fixed surface 63. In the radial direction of the inner circumferential surface 60, the distance between the center line C1 and the fixed surface 63 is greater than the distance between the center line C1 and the fixed surface 64. In the radial direction of the inner circumferential surface 60, the distance between the center line C1 and the fixed surface 64 is greater than the distance between the center line C1 and the fixed surface 65.

[0027] The fixed surface 61 faces the rotating surface 51 in the radial direction of the rotating shaft 20. The fixed surface 62 faces the rotating surface 52 in the radial direction of the rotating shaft 20. The fixed surface 63 faces the rotating surface 53 in the radial direction of the rotating shaft 20. The fixed surface 64 faces the rotating surface 54 in the radial direction of the rotating shaft 20. The fixed surface 65 faces the rotating surface 54 in the radial direction of the rotating shaft 20.

[0028] [Fin70] The seal structure 40 has a plurality of fins 70. The plurality of fins 70 include fins 71 to 75. Fins 71 project radially from the fixed surface 61 toward the rotating surface 51. A plurality of fins 71 are formed on the fixed surface 61. The plurality of fins 71 are arranged at intervals in the axial direction of the rotating shaft 20. There may be just one fin 71.

[0029] The fins 72 project radially from the fixed surface 62 toward the rotating surface 52. Multiple fins 72 are formed on the fixed surface 62. The multiple fins 72 are spaced apart in the axial direction of the rotating shaft 20. There may be just one fin 72.

[0030] The fins 73 project radially from the fixed surface 63 toward the rotating surface 53. Multiple fins 73 are formed on the fixed surface 63. The multiple fins 73 are spaced apart in the axial direction of the rotating shaft 20. There may be just one fin 73.

[0031] The fins 74 project radially from the fixed surface 64 toward the rotating surface 54. Multiple fins 74 are formed on the fixed surface 64. The multiple fins 74 are spaced apart in the axial direction of the rotating shaft 20. There may be just one fin 74.

[0032] The fins 75 project radially from the fixed surface 65 toward the rotating surface 55. Multiple fins 75 are formed on the fixed surface 65. The multiple fins 75 are spaced apart in the axial direction of the rotating shaft 20. There may be just one fin 75.

[0033] [Width between fins W] The width W11 between fins 71 and 72 shown in Figure 3 is the distance between the fin 71 closest to the lowest pressure space and the fin 72 closest to the highest pressure space. The width W12 between fins 72 and 73 is the distance between the fin 71 closest to the lowest pressure space and the fin 73 closest to the highest pressure space. The width W12 on the low-pressure side is narrower than the width W11 on the high-pressure side. The width W12 may also be 90% of the width W11. Note that the high-pressure space side is closer to the high-pressure space than the low-pressure space.

[0034] The width W13 between fins 73 and 74 shown in Figure 4 is the distance between the fin 73 closest to the lowest pressure space and the fin 74 closest to the highest pressure space. The width W13 on the low-pressure side is narrower than the width W12 on the high-pressure side. The width W13 may also be 90% of the width W12.

[0035] The width W14 between fins 74 and 75 is the distance between the fin 74 closest to the lowest pressure space and the fin 75 closest to the highest pressure space. The width W14 on the low-pressure side is narrower than the width W13 on the high-pressure side. The width W14 may also be 90% of the width W13. The widths W11 to W14 become shorter as you move towards the low-pressure side (downstream side).

[0036] [Length L between the fin on the low-pressure side and the end] The length L11 between the fin 71 and the end 81 shown in Figure 3 is the length between the fin 71 on the lowest pressure side of the multiple fins 71 and the end 81 on the low pressure side of the rotating surface 51. The end 81 is an end face that is aligned with the radial direction of the rotation axis 20.

[0037] The length L12 between the fin 72 and the end 82 is the length between the fin 72 closest to the low-pressure space among the multiple fins 72 and the end 82 on the low-pressure space side of the rotating surface 52. The end 82 is an end face that is aligned with the radial direction of the rotation axis 20.

[0038] The length L13 between the fin 73 and the end 83 shown in Figure 4 is the length between the fin 74 on the lowest pressure side of the multiple fins 73 and the end 83 on the low pressure side of the rotating surface 53. The end 83 is an end face that is aligned with the radial direction of the rotation axis 20.

[0039] The length L14 between the fin 74 and the end 84 is the length between the fin 74 closest to the low-pressure space among the multiple fins 74 and the end 84 on the low-pressure space side of the rotating surface 54. The end 84 is an end face that is aligned with the radial direction of the rotation axis 20.

[0040] The lengths L11, L12, L13, and L14 in the axial direction may be equal.

[0041] [Effects of the turbo compressor 100 according to the embodiment] The turbo compressor 100 according to this embodiment is a rotating machine comprising an impeller (rotating body) 10, a rotating shaft 20 that drives the impeller 10, a casing 30 that houses the impeller 10 and the rotating shaft 20, and a sealing structure 40 that seals the gap between the impeller 10 and the casing 30. In the casing 30, a high-pressure space HP is formed on one side in the axial direction of the impeller 10 (the direction in which the center line C1 extends), and a low-pressure space LP is formed on the other side in the axial direction of the impeller 10. The outer circumferential surface 50 of the impeller 10 has, in order from the high-pressure space HP side, a rotating surface (first rotating surface) 51, a rotating surface (second rotating surface) 52, and a rotating surface (third rotating surface) 53. The distance of the rotating surface 51 from the center line C1 is greater than the distance of the rotating surface (second rotating surface) 52 from the center line C1. The distance from the center line C1 of the rotating surface (second rotating surface) 52 is greater than the distance from the center line C1 of the rotating surface (third rotating surface) 53. The casing 30 has a fixed surface (first fixed surface) 61 facing the rotating surface 51, a fixed surface (second fixed surface) 62 facing the rotating surface 52, and a fixed surface (third fixed surface) 63 facing the rotating surface 53. The casing 30 has one or more fins (first fins) 71 projecting from the fixed surface 61 toward the rotating surface 51 and spaced apart in the axial direction, one or more fins (second fins) 72 projecting from the fixed surface 62 toward the rotating surface 52 and spaced apart in the axial direction, and one or more fins (third fins) 73 projecting from the fixed surface 63 toward the rotating surface 53 and spaced apart in the axial direction. The seal structure 40 includes the fins 71 to 73. The axial distance between one or more fins 71, the fin 71 closest to the lowest pressure space (LP), and one or more fins 72, the fin 72 closest to the highest pressure space (HP), is defined as the width (first width) W11. The axial distance between one or more fins 72, the fin 72 closest to the lowest pressure space (LP), and one or more fins 73, the fin 73 closest to the highest pressure space (HP), is defined as the width (second width) W12. The width W12 on the low-pressure space (LP) side is narrower than the width W11 on the high-pressure space (HP) side.

[0042] In such a turbo compressor 100, the gap between the fins 70 can be narrowed in the axial direction of the rotating shaft 20 from the high-pressure side to the low-pressure side. The width W12 between fin 72 and fin 73 is narrower than the width W11 between fin 71 and fin 72. The width W13 between fin 73 and fin 74 is narrower than the width W12 between fin 72 and fin 73. The temperature of the refrigerant in the high-pressure space HP is higher than the temperature of the refrigerant in the low-pressure space LP. The temperature at the outlet side of the impeller 10 is higher than the temperature at the inlet side.

[0043] In the seal structure 40, the widths W11 to W14 narrow as they move toward the low-pressure space LP. As a result, the axial velocity of the fluid after passing through the fin closest to the low-pressure space LP increases as it moves toward the low-pressure space. Therefore, the fluid that has passed through collides with the fin closest to the high-pressure space HP on the next surface (the inner circumferential surface on the downstream side), improving the hydrostatic pressure recovery effect of the fluid and enhancing the sealing performance.

[0044] Furthermore, in the seal structure 40, the width W12 between fins 72 and 73 on the low-pressure space LP side can be made narrower than the width W11 between fins 71 and 72 on the high-pressure space HP side, thereby preventing contact due to thermal contraction in the axial direction and improving sealing performance. "Contact due to thermal contraction" may also refer to contact between the fins and ends 81-84 in the axial direction. In the turbo compressor 100, the widths W11-W14 can be made narrower as you move towards the low-pressure side (downstream side). Also, the temperature distribution inside the impeller 10 becomes lower as you move towards the low-pressure space LP side and higher as you move towards the high-pressure space HP. As a result, the dimensional change due to thermal contraction of the impeller 10 itself is such that the width W11 narrows and the width W14 widens, which is the opposite relationship to the seal structure 40, making contact due to thermal contraction less likely. In addition, by making the seal structure 40 compact, contact is less likely to occur during thermal contraction inside the impeller 10.

[0045] Furthermore, since the meridional shape of the impeller 10 is curved, making it compact makes it easier to form a seal structure on the impeller 10. Compared to conventional technology, the seal structure 40 allows for a shorter seal length in the axial direction, thereby improving sealing performance. This turbo compressor 100 reduces pressure imbalance in the circumferential direction caused by the oscillation of the impeller 10, thereby suppressing the generation of destabilizing forces.

[0046] The turbo compressor 100 includes an impeller 10, which is a closed impeller, as a rotating body attached to the rotating shaft 20. Generally, the seal diameter of the seal structure used in the shroud portion of a closed impeller is larger than the seal diameter of the seal structure on the rotating shaft (shaft seal). In the seal structure of the shroud portion of a closed impeller, the lower limit of the seal gap is larger than that of the shaft seal from the viewpoint of rotor dynamics and runout. Therefore, in the shroud portion of a closed impeller, the seal area becomes excessively large compared to the shaft seal, and the sealing performance tends to deteriorate. By adopting the seal structure 40 of this disclosure in the shroud 13 of a closed impeller, the deterioration of sealing performance can be suppressed.

[0047] Furthermore, in the turbo compressor 100, the length (first length) L11 between the fin 71 on the lowest pressure space LP side of one or more fins 71 and the end 81 on the low pressure space LP side of the rotating surface 51 in the axial direction, the length (second length) L12 between the fin 72 on the lowest pressure space LP side of one or more fins 72 and the end 82 on the low pressure space LP side of the rotating surface 52 in the low pressure space LP side, and the length (third length) L13 between the fin 73 on the lowest pressure space LP side of one or more fins 73 and the end 83 on the low pressure space LP side of the rotating surface 53 in the low pressure space LP side may be equal. By making the lengths L11, L12, and L13 equal in the seal structure 40, the sealing performance can be improved.

[0048] Furthermore, in the turbo compressor 100, the rotating surfaces 51-55 are parallel to the axial direction, and the cross-section perpendicular to the rotating surfaces 51-55 may be circular. Such a seal structure 40 can improve sealing performance and reduce pressure imbalance in the circumferential direction due to the wobble of the rotating body, thereby suppressing the generation of destabilizing forces. In such a seal structure 40, the radial flow path opposite the fins 70 is formed in a uniform cylindrical shape. The radial width can be made uniform in the flow path that is continuous in the circumferential direction along the rotating surfaces 51-55. The gap G between the outer circumferential surface 50 and the inner circumferential surface 60 can be made uniform in the circumferential direction. As a result, the sealing performance of the seal structure 40 can be improved and destabilizing forces can be reduced.

[0049] In this embodiment, the rotating machine having the seal structure 40 is a turbo compressor 100. Generally, in turbo compressors that operate at high absolute pressures, the adoption of the seal structure 40 improves sealing performance and reduces destabilizing forces by shortening the axial length of the seal structure 40. The turbo compressor may be centrifugal or mixed-flow.

[0050] [Effects of the refrigeration system 110 equipped with a turbo compressor 100 according to the embodiment] Next, a refrigeration system 110 equipped with a turbo compressor 100 according to an embodiment will be described. Figure 5 is a schematic diagram showing a refrigeration system 110 equipped with a turbo compressor according to an embodiment. The refrigeration system 110 shown in Figure 5 can be used, for example, in air conditioning systems, refrigeration equipment, and refrigerator equipment. The refrigeration system 110 may be used in other equipment. The refrigeration system 110 performs a refrigeration cycle. The refrigeration cycle of the refrigeration system 110 is a vapor compression refrigeration cycle. The refrigeration system 110 comprises a turbo compressor 100, a condenser 120, an expansion valve 130, and an evaporator 140. The refrigeration system 110 may also be a refrigerator.

[0051] The refrigerant, which is the working fluid of the refrigeration system 110, is not particularly limited. The turbo compressor 100 compresses the refrigerant gas. The condenser 120 condenses the refrigerant gas compressed by the turbo compressor 100. The expansion valve 130 expands the refrigerant condensed by the condenser 120. The evaporator 140 evaporates the refrigerant expanded by the expansion valve 130. The refrigerant gas evaporated in the evaporator 140 is drawn into the turbo compressor 100.

[0052] The turbo compressor 100 reversibly adiabatically compresses the refrigerant gas. The refrigerant gas supplied to the condenser 120 releases heat at a constant pressure and liquefies. The liquefied refrigerant irreversibly expands at a constant enthalpy in the expansion valve 130, causing a portion of the refrigerant to evaporate. The refrigerant absorbs heat at a constant pressure in the evaporator 140.

[0053] The refrigeration system 110 is equipped with piping L101 to L104 through which the refrigerant flows. Piping L101 is an intake pipe connecting the evaporator 140 and the turbo compressor 100. Piping L102 connects the turbo compressor 100 and the condenser 120. Piping L103 connects the condenser 120 and the expansion valve 130. Piping L104 connects the expansion valve 130 and the evaporator 140.

[0054] The refrigerant gas flows through piping L101 and is drawn into the turbo compressor 100. The refrigerant gas compressed by the turbo compressor 100 flows through piping L102 and is supplied to the condenser 120. The refrigerant liquid liquefied in the condenser 120 flows through piping L103 and flows into the expansion valve 130. The refrigerant expanded in the expansion valve 130 flows through piping L104 and is supplied to the evaporator 140. The refrigerant gas that has absorbed heat in the evaporator 140 flows through piping L101 and is supplied to the turbo compressor 100.

[0055] [Control Unit 210] The control unit 210 includes a CPU and a memory unit. The CPU (Center Processing Unit) is responsible for the overall processing in the refrigeration system 110. The CPU can control the rotational speed of the motor 340 via the inverter 80. The CPU 210 can control the opening and closing operation of the expansion valve 130. The control unit 210 can control the operation of the magnetic bearing.

[0056] The memory unit includes ROM (Read Only Memory) and RAM (Random Access Memory). The ROM stores various programs for the CPU to execute control processing, as well as various data necessary for the operation of the refrigeration system 110. The RAM can temporarily store data acquired from various sensors.

[0057] Thus, in a refrigeration system 110 that performs a refrigeration cycle that circulates a refrigerant, a turbo compressor 100 employing the above-described seal structure 40 can be used. Turbo compressors 100 used in refrigeration systems have high differential pressures and require improved sealing performance, and in the refrigeration system 110, improved sealing performance is achieved by incorporating the above-described turbo compressor 100.

[0058] In a refrigeration system 110 that performs a refrigeration cycle circulating a refrigerant, the absolute pressure required for operation is high. Therefore, by employing a seal structure 40, it is possible to improve sealing performance and reduce destabilizing forces by shortening the axial length of the seal structure 40.

[0059] [Bearing of the turbo compressor 100 according to the embodiment] Next, the bearings 331 to 334 of the turbo compressor 100 will be described. Figure 6 is a cross-sectional view showing the 100 according to an embodiment. The turbo compressor 100 includes bearings 331 to 334 that rotatably support the rotating shaft 20. The bearings 331 to 334 are fixed to the casing 30. Bearings 331 and 332 are radial magnetic bearings, and bearings 333 and 334 are thrust magnetic bearings.

[0060] The bearings 331 to 334 may be magnetic bearings that support the rotating shaft using magnetic attraction or repulsion. The bearings 331 to 334 may also be active magnetic bearings (AMB). The radial magnetic bearing includes an electromagnet arranged around the rotating shaft 20. The electromagnet has an iron core and a coil. The thrust magnetic bearing includes an axial disk 21 that protrudes radially outward from the rotating shaft 20, and an electromagnet arranged to face the axial disk 21 in the axial direction. The axial disk 21 is provided at end 20b of the rotating shaft 20. End 20a of the rotating shaft 20 is the end closer to the impeller 10, and end 20b is the end further away from the impeller 10.

[0061] Bearings 331-334 are, for example, oil-less bearings. Bearings 331 and 332 may be sliding bearings or rolling bearings. Bearings 331-334 may also be hydrostatic bearings. Oil-less bearings are bearings that do not require the supply of lubricating oil. Examples of oil-less bearings include gas bearings, air bearings, foil bearings, and magnetic bearings.

[0062] Bearings 331 to 334 may be pneumatic bearings. Pneumatic bearings are a type of hydrostatic bearing, and compressed air is blown between the rotating shaft 20 and the bearing surface to levitate the rotating shaft 20 with air pressure and support the load. Bearings 331 and 332 may also be gas bearings that levitate the rotating shaft 20 by blowing compressed gas between the rotating shaft 20 and the bearing surface. Gas bearings may also levitate the rotating shaft 20 by blowing a refrigerant gas as the compressed gas.

[0063] The bearings 331 to 334 may be foil bearings, which are a type of pneumatic bearing. A foil bearing has a thin film (foil) as the bearing surface. The thin film has low rigidity against bending and is flexible. The foil bearing supports the load by allowing the deflection of the foil. When the rotating shaft 20 rotates, a fluid film (air film) is formed between the rotating shaft 20 and the bearing surface, which is the foil. The foil bearing supports the rotating shaft 20 using the foil and the fluid film. Due to the flexibility of the foil, the foil bearing can form a bearing clearance that corresponds to the rotational speed of the rotating shaft 20, the load on the rotating shaft 20, the ambient temperature around the rotating shaft 20, and other operating conditions.

[0064] The types, locations, and quantities of bearings 331-334 are not limited to those described above. The turbo compressor 100 may be equipped with touchdown bearings. Touchdown bearings are also called auxiliary bearings or backup bearings. Touchdown bearings limit the range of motion of the rotating shaft 20. Touchdown bearings can limit the range of motion of the rotating shaft 20 in the radial direction. Touchdown bearings can limit the range of motion of the rotating shaft 20 in the axial direction. Touchdown bearings can prevent contact between the stator and the rotor. Touchdown bearings can support the rotating shaft 20 when the magnetic bearings are not energized.

[0065] In a turbo compressor 100 equipped with a magnetic bearing, the above-described seal structure 40 can be used to reduce the destabilizing force by shortening the axial length of the seal structure 40, thus providing an advantageous structure for magnetic bearings, which are susceptible to vibration forces on the shaft. In rotating machinery equipped with magnetic bearings, destabilizing forces tend to be a problem, but in the turbo compressor 100, the above-described seal structure 40 reduces the destabilizing force by shortening the axial length of the seal structure.

[0066] [Motor 340] As described above, the turbo compressor 100 includes a motor 340. The motor 340 is the driving source for the turbo compressor 100. The motor 340 has a rotor 341 and a stator 342. The rotor 341 is fixed to the rotating shaft 20 and rotates with the rotating shaft 20. The stator 342 is fixed to the casing 30 and is positioned around the rotor 341.

[0067] [Casing 30] The casing 30 houses the impeller 10, the rotating shaft 20, the bearings 331-334, and the motor 340. The casing 30 has a compression chamber 30a for housing the impeller 10, a motor chamber 30b for housing the rotating shaft 20, the bearings 331-334, and the motor 340, and a partition wall 30c between the compression chamber 30a and the motor chamber 30b.

[0068] A diffuser 362 is formed in the compression chamber 30a. The diffuser 362 is formed on the outside of the impeller 10 in the radial direction of the impeller 10.

[0069] The casing 30 has an intake port 352 into which the refrigerant flows. The intake port 352 extends in the axial direction of the rotating shaft 20. The refrigerant that flows through the intake port 352 is supplied to the impeller 10. The refrigerant compressed by the impeller 10 flows through the diffuser 362 and is exhausted from the turbo compressor 100.

[0070] [Seal structure 40B related to a modified example] The turbo compressor 100 may be equipped with a modified seal structure 40B. The seal structure 40 is not limited to being provided on the shroud 13 of the impeller 10, but may be provided at other locations. The seal structure 40B may seal the gap between the rotating shaft 20 and the casing 30. The seal structure 40B can seal the gap between the partition wall 30c and the rotating shaft 20.

[0071] The seal structure 40 is not limited to that provided in the turbo compressor 100, but may also be provided in other rotating machinery such as compressors and pumps.

[0072] [Seal structure 40 according to the second embodiment] Figure 7 is a cross-sectional view showing the seal structure 40 according to the second embodiment. The difference between the seal structure 40 according to the second embodiment shown in Figure 7 and the seal structure 40 according to the first embodiment shown in Figure 2 is that the number of rotating surfaces and the number of fixed surfaces are different. Note that in the description of the second embodiment, explanations similar to those for the first embodiment described above may be omitted.

[0073] The outer circumferential surface 50 of the rotating body 10 has a first rotation surface 51, a second rotation surface 52, and a third rotation surface 53, in order from the high-pressure space HP side. The distance of the first rotation surface 51 from the center line C1 of the rotation axis 20 is greater than the distance of the second rotation surface 52 from the center line C1 of the rotation axis 20. The distance of the second rotation surface 52 from the center line C1 of the rotation axis 20 is greater than the distance of the third rotation surface 53 from the center line C1 of the rotation axis 20.

[0074] The casing 30 has a first fixed surface 61 facing the first rotating surface 51, a second fixed surface 62 facing the second rotating surface 52, a third fixed surface 63 facing the third rotating surface 53, one or more first fins 71 projecting from the first fixed surface 61 toward the rotating body 10 and spaced apart in the axial direction, one or more second fins 72 projecting from the second fixed surface 52 toward the rotating body 10 and spaced apart in the axial direction, and one or more third fins 73 projecting from the third fixed surface 63 toward the rotating body 10 and spaced apart in the axial direction.

[0075] As shown in Figure 3, the seal structure 40 includes a first fin 71, a second fin 72, and a third fin 73. The axial distance between the first fin 71 on the lowest pressure space (LP) side of one or more first fins 71 and the second fin 72 on the highest pressure space (HP) side of one or more second fins 72 is defined as the first width W11. The axial distance between the second fin 72 on the lowest pressure space (LP) side of one or more second fins 72 and the third fin 73 on the highest pressure space (HP) side of one or more third fins 73 is defined as the second width W12. The second width W12 is narrower than the first width W11.

[0076] A rotating machine 100 equipped with the seal structure 40 according to the second embodiment provides the same effects and advantages as a rotating machine 100 equipped with the seal structure 40 according to the first embodiment.

[0077] The number of rotating surfaces may be three, four, or five or more. The number of fixed surfaces may be three, four, or five or more. The number of first fins 71 formed on the first fixed surface 61 may be one or more. The number of second fins 72 formed on the second fixed surface 62 may be one or more. The number of third fins 73 formed on the third fixed surface 63 may be one or more.

[0078] Preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the embodiments described above. Various modifications, substitutions, etc., can be applied to the embodiments described above without departing from the scope of the present invention. Furthermore, features described separately can be combined as long as no technical inconsistencies arise.

[0079] The above embodiment illustrates a refrigeration system 110 equipped with a turbo compressor 100, but the turbo compressor 100 can be applied to applications other than the refrigeration system 110. The internal fluid of the turbo compressor 100 is not limited to a refrigerant.

[0080] The turbo compressor 100 described above illustrates the case where lengths L11 to L14 are constant, but lengths L11 to L14 may be different.

[0081] The turbo compressor 100 described above illustrates the case where the rotational surfaces 51-55 are modified with respect to the axial direction (centerline C1). However, the rotational surfaces 51-55 do not have to be parallel to the axial direction. For example, in a cross-section along the axial direction, the rotational surfaces 51-55 may be inclined with respect to the axial direction.

[0082] The combination of the first and second widths can be widths W11 and W12, W12 and W13, or W13 and W14.

[0083] For example, in the axial direction, the lengths of the rotating surfaces 51 to 54 may be the same. In the axial direction, the length of the downstream rotating surface 55 may be longer than the lengths of the rotating surfaces 51 to 54 upstream of rotating surface 55.

[0084] For example, the spacing between the multiple fins 71 formed on the fixed surface 61 may be equal or uneven. The spacing between the multiple fins 71 may be narrower than the width W11.

[0085] One aspect of the present invention may be as follows:

[0086] <1> A solid of rotation and A rotating shaft that drives the aforementioned rotating body, A casing that houses the rotating body and the rotating shaft, A sealing structure that seals the gap between the rotating body and the casing, A rotating machine equipped with, In the casing, a high-pressure space is formed on one side in the axial direction of the rotating body, and a low-pressure space is formed on the other side in the axial direction of the rotating body. The outer circumferential surface of the rotating body has, in order from the high-pressure space side, a first rotation surface, a second rotation surface, and a third rotation surface. The distance of the first rotational surface from the axis of rotation is greater than the distance of the second rotational surface from the axis of rotation. The distance of the second rotational surface from the axis of rotation is greater than the distance of the third rotational surface from the axis of rotation. The aforementioned casing is A first fixed surface facing the first rotating surface, A second fixed surface facing the second rotating surface, A third fixed surface facing the third rotating surface, One or more first fins project from the first fixed surface toward the rotating body and are spaced apart in the axial direction, One or more second fins project from the second fixed surface toward the rotating body and are spaced apart in the axial direction, It has one or more third fins that protrude from the third fixed surface toward the rotating body and are spaced apart in the axial direction, The seal structure includes the first fin, the second fin, and the third fin. The distance in the axial direction between the first fin, which is the one or more first fins closest to the low-pressure space, and the second fin, which is the one or more second fins closest to the high-pressure space, is defined as the first width. The distance in the axial direction between the second fin on the lowest pressure side of the one or more second fins and the third fin on the highest pressure side of the one or more third fins is defined as the second width. A rotating machine in which the second width is narrower than the first width. <2> The rotating body is a closed impeller. The above <1> The rotating machinery described above. <3> In the axial direction, the first length between the first fin on the lowest pressure side of the one or more first fins and the end of the first rotation surface on the low pressure side, the second length between the second fin on the lowest pressure side of the one or more second fins and the end of the second rotation surface on the low pressure side, and the third length between the third fin on the lowest pressure side of the one or more third fins and the end of the third rotation surface on the low pressure side are equal to the above <1> or <2> The rotating machinery described above. <4> The first plane of rotation, the second plane of rotation, and the third plane of rotation are parallel to the axial direction. The cross-sections perpendicular to the axial direction of the first, second, and third rotational planes are circular. The above <1> ~ <3> A rotating machine as described in any one of the following. <5> The above-mentioned rotating shaft is provided with a magnetic bearing that rotatably supports the rotating shaft. <1> ~ <4> A rotating machine as described in any one of the following. <6> The above <1> ~ <5> A turbo compressor, which is a rotating machine as described in any one of the following documents. <7> The above <6> A refrigeration system equipped with a turbo compressor as described above. [Explanation of Symbols]

[0087] 100 Turbo Compressor 110 Refrigeration System 10 Impeller (rotating body) 13 Shroud 20. Rotating axis (rotating body) 30 Casing 40,40B seal structure 50 Outer surface of the impeller 51-55 Planes of rotation (1st plane of rotation, 2nd plane of rotation, 3rd plane of rotation) 60 Inner surface 61~65 Fixed surface (1st fixed surface, 2nd fixed surface, 3rd fixed surface) 70 fins 71-75 fins (1st fin, 2nd fin, 3rd fin) 81-84 End 331-334 Bearings (magnetic bearings) HP High Pressure Space LP Low-voltage space L11~L14 Length (1st length, 2nd length, 3rd length) W11~W14 Width (1st width, 2nd width)

Claims

1. Rotating body (10) and A rotating shaft (20) that drives the rotating body, A casing (30) housing the rotating body and the rotating shaft, A sealing structure (40) that seals the gap between the rotating body and the casing, A rotating machine (100) equipped with, In the casing, a high-pressure space (HP) is formed on one side in the axial direction of the rotating body, and a low-pressure space (LP) is formed on the other side in the axial direction of the rotating body. The outer circumferential surface of the rotating body has, in order from the high-pressure space side, a first rotation surface (51), a second rotation surface (52), and a third rotation surface (53). The distance of the first rotational surface from the axis of rotation is greater than the distance of the second rotational surface from the axis of rotation. The distance of the second rotational surface from the axis of rotation is greater than the distance of the third rotational surface from the axis of rotation. The aforementioned casing is A first fixed surface (61) facing the first rotating surface, A second fixed surface (62) facing the second rotating surface, A third fixed surface (63) facing the third rotating surface, One or more first fins (71) protrude from the first fixed surface toward the rotating body and are arranged at intervals in the axial direction, One or more second fins (72) protrude from the second fixed surface toward the rotating body and are arranged at intervals in the axial direction, It has one or more third fins (73) that protrude from the third fixed surface toward the rotating body and are spaced apart in the axial direction, The sealing structure includes the first fin, the second fin, and the third fin. The distance in the axial direction between the first fin, which is the one or more first fins closest to the low-pressure space, and the second fin, which is the one or more second fins closest to the high-pressure space, is defined as the first width (W11). The distance in the axial direction between the second fin on the lowest pressure side of the one or more second fins and the third fin on the highest pressure side of the one or more third fins is defined as the second width (W12). A rotating machine in which the second width is narrower than the first width.

2. The rotating body is a closed impeller. The rotating machine according to claim 1.

3. The rotating machine according to claim 1 or 2, wherein, in the axial direction, the first length (L11) between the first fin on the lowest pressure side of the one or more first fins and the end (81) of the first rotating surface on the low pressure side is equal to the second length (L12) between the second fin on the lowest pressure side of the one or more second fins and the end (82) of the second rotating surface on the low pressure side is equal to the third fin (L13) on the lowest pressure side of the one or more third fins and the end (83) of the third rotating surface on the low pressure side is equal to the third rotating machine according to claim 1 or 2.

4. The first plane of rotation, the second plane of rotation, and the third plane of rotation are parallel to the axial direction. The cross-sections perpendicular to the axial directions of the first, second, and third rotational planes are circular. The rotating machine according to claim 1 or 2.

5. The rotating machine according to claim 1 or 2, further comprising magnetic bearings (331-334) that rotatably support the rotating shaft.

6. A turbo compressor, which is a rotating machine according to claim 5.

7. A refrigeration system (110) comprising a turbo compressor according to claim 6.

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